python - 当我调用以下名为 find_element_by_xpath 的函数时到底发生了什么？

Question

我对以下方法有疑问..

 driver.find_element_by_xpath

当我通过 ide 导航时，我遇到了以下调用。 ->

def find_element_by_xpath(self, xpath):
        """
        Finds an element by xpath.

        :Args:
         - xpath - The xpath locator of the element to find.

        :Usage:
            driver.find_element_by_xpath('//div/td[1]')
        """
        return self.find_element(by=By.XPATH, value=xpath)

然后当我导航到“find_element”时，我得到以下内容

def find_element(self, by=By.ID, value=None):
        """
        'Private' method used by the find_element_by_* methods.

        :Usage:
            Use the corresponding find_element_by_* instead of this.

        :rtype: WebElement
        """
        if not By.is_valid(by) or not isinstance(value, str):
            raise InvalidSelectorException("Invalid locator values passed in")
        if self.w3c:
            if by == By.ID:
                by = By.CSS_SELECTOR
                value = '[id="%s"]' % value
            elif by == By.TAG_NAME:
                by = By.CSS_SELECTOR
            elif by == By.CLASS_NAME:
                by = By.CSS_SELECTOR
                value = ".%s" % value
            elif by == By.NAME:
                by = By.CSS_SELECTOR
                value = '[name="%s"]' % value
        return self.execute(Command.FIND_ELEMENT,
                             {'using': by, 'value': value})['value']

最后我得到了以下内容

def execute(self, driver_command, params=None):
    """
    Sends a command to be executed by a command.CommandExecutor.

    :Args:
     - driver_command: The name of the command to execute as a string.
     - params: A dictionary of named parameters to send with the command.

    :Returns:
      The command's JSON response loaded into a dictionary object.
    """
    if self.session_id is not None:
        if not params:
            params = {'sessionId': self.session_id}
        elif 'sessionId' not in params:
            params['sessionId'] = self.session_id

    params = self._wrap_value(params)
    response = self.command_executor.execute(driver_command, params)
    if response:
        self.error_handler.check_response(response)
        response['value'] = self._unwrap_value(
            response.get('value', None))
        return response
    # If the server doesn't send a response, assume the command was
    # a success
    return {'success': 0, 'value': None, 'sessionId': self.session_id}

当我如下使用此功能时

apply = driver.find_element_by_xpath("//*@id='maincontent']/form/div[3]/input")

这里我存储了要应用的该函数的返回值以及当我查找类型(应用)时的返回值。我得到以下类型

<class 'selenium.webdriver.remote.webelement.WebElement'>

即使我也能够对类方法执行多个相同的操作，如下所示

driver.find_element_by_xpath("//*[@id='cbid.vpn-g.VPN_Type.type']").find_element_by_id("cbi-vpn-g-VPN_Type-type-pptp").click()

谁能给我解释一下吗？

Answer 1

find_element_by_xpath() 和其他 find_element_by_* 方法基本上是主 find_element() 方法的便捷快捷方式/包装器，该方法将发送 findElement WebDriver command通过 JSON Wire protocol(基于 HTTP 的 RESTful JSON)。

如果找到一个元素，find_element() 返回一个 WebElement 实例，该实例本身具有上述所有方法并表示一个 DOM 元素。如果指定的定位器未找到某个元素，则会抛出 NoSuchElementException。